Spark plug



Oct. 12,1937. w. E. BLOOD I 2,095,540

SPARK PLUG Filed Jan. 8, 1937 INVENTOR. WIHICIm'E. Bloc I 4, ,Ql

ATTORNEY.

. ;the present invention, the lower portion of the srn PLUG William E.-Blood, New'York, N. Y. Application January 8, 1937, Serial No. 1l9,58

8 Claims. (e1. l23lt9) 10 of the plug.

The present invention provides a simple and efiicient means for accomplishing this result and .is adapted to be employed in spark plugs of practically all kinds where'this problem is inl5 volved.

Speaking generally, incorporatinginto the wall of the shell, a series of inlays extending longitudinally of the shell, in good heatconductive relation withthe ground 20 electrode and adapted toalso have good heat conductive relation with the tapped hole in the cylinder block into which the plug is screwed. These inlays are of a metal of high heat conductivity and they are thus adapted to efficiently 25 carry off the heat from theground electrode and transfer it to the cylinder block where it is dissipated. The inlays maybe made in any number s and size to meet requirements of any particular plug and will effectually preclude the ground 'elec- 3 trode from overheating and causing pre-ignition.

Features of the invention, other than those adverted to, will be apparent from the hereinafter detailed description and claims, when read in conjunction with the accompanying drawing.

The accompanying drawing illustrates difierent practical embodiments of the invention, but the constructions therein shown are to be understood as illustrative, only, and not as defining the limits of the invention.

Figure l is a side elevation of aplug embodying disclose the structure thereof. I v

. plug being shown in central section to more clearly .Figure 2 is a section through the shell of the, l ,45 plug on theline 2-2 of l 'igure 1.

Figure 3 is a side elevation of the lower end portion-of the plug shell shown in Figures 1 and Figure' l is a view similar to Figure 2, but illus- 50 tratlng amodlfied form of construction.

The plug shown in Figure 1 is, in the main, substantially conventional, the chief departure from ordinary construction being in the shell portion l thereof. This shell may be of any 55 appropriate shape and the electrode 2 associthe invention consists in Y ated therewith may be also of any suitable kind,

although it is shown in the form of a baflle plate, welded or otherwise secured to the lower end of the shell and provided with inwardly extending fingers 3 adapted to form, with the spindle head i, the spark gaps of the plug. I

In incorporating the invention in a plug of this kind, I form, in the outer face of the threaded shank 5 of the shell, a series of longitudinal grooves, channels or recesses B of any appropriate number and these recesses are made deeper in proximity, with the ground electrode 2, as indicated at F. In each of these grooves Iplace an inlay 8, which is preferably of copper, brass or some other metal of higher heat conductivity than the metal of the shell 5 or the metal of the electrode 2. Copper may be conveniently used for this purpose, because. it can be readily worked and it is a remarkably good heat conductor. The inlays are preferably madeibefore the shank 5 is threaded and the threading is carried out after the inlays have been completed, so that the threads are cut through the inlays and in the shank. Consequently when the plug is screwed into the spark plug hole of a cylinder block, the

I threaded portions of the inlays make direct contact-with the wall of the cylinder block and by virtue of the deepening of the recesses at 1, these inlays also have anappreciable contact area with the ground electrode 2.

There is thus provided a direct path for the conduction of heat, through high heat conductive material, from. the electro e 2 to the cylinder block and thiswill efiectually protect the electrode 2 from overheating. .The recesses or channels in which the inlays are placed may, be undercut or of any other appropriate cross section, so as to properlyjmaintain the inlays in position.

In Figure 2 the channels are shown, with substantially straight sides and the inlays maybe brazed, plated, ,or otherwise, secured in these channels, although they may be simply forced into place under considerable pressure,

In Figure l the channels are shown as circular and are arranged substantially tangent ,to the outer periphery of the shank 5 and may conveniently be formed by boring circular holes 9, as shown. Into these holes, metal of high heat conductivity is introduced in any suitable way, as by pouring or forcing it into place, to form. the in-- lays.

The inlays-need not necessarily have a homogeneous bond with the shell, although they may have if desired, and they need not have a homogeneous bond with the electrode, although they preferably have, so as to insure a good heat transfer between the electrode and the inlays. This bond may be produced by soldering or brazing or otherwise.

In prior practice, it has generally been sought to conduct the heat from the ground electrode to the shell and then conduct it through the shell to the cylinder block. In accordance with the present invention, in contradistinction, it is not the purpose of conducting the heat from the electrode to the shell, but rather to conduct the heat from the electrode, through the inlays, to the cylinder block, so that the shell is not depended upon as a heat carrier, but serves in a large measure merely to serve as a support for the inlays which actually form the heat bridge between the electrode and the cylinder block. Therefore I amnot particularly concerned with the relation between the electrode and the shell other than that the shell must properly support the electrode, but I am primarily concerned with a proper heat path interposed substantially direct-" ly between the electrode and the cylinder block.

In carrying out the present invention in practice, it is desirable in every instance thatthe inlays should be so positioned that they are protected against the unrestricted action of the buming combustion charge upon them. In other words, they should not be open and exposed to the burning charge for if this is permitted, they will tend to take up the heat directly from the charge rather than to draw heat from the ground electrode. Consequently they are positioned above the baiile and are so protected by the lower end of the plug that .the burning combustion charge does notdirectly contact with them.

In bothof--the' constructions which I have shown the inlays are at-the outer surface of the shell, so that the threads 'are cut through said inlays. I may, however, form the channels at the base of the threads, so that the threads do not I cut through the inlaysl. The inlays should, how-- ever, be so close to the outer surface of the shell that the intervening material of the shell will not appreciably retard'the transfer of heat to the cylinder block. This should be borne in mind in the consideration of the appended claims, where, in I have referred to the inlays as in proximity to the outer surface of the shank to mean either at or closely adjacent thereto. r

The foregoing detailed description sets forth the invention in the preferred practical forms;

. but'the invention is to be understood as fully s5shank audin proximity to the outer surface thereof.

2.Asparkplug comprisingaahellhaviuga threaded shank adapted to be screwed into the spark plug hole of a cylinderblock and provided in proximity to the outer surface of the shank with longitudinal inlays of metal of higher heat conductivity than the metal of the shell, and a ground electrode secured to the lower end of the shank and in good heat conducting relation to the lower ends of the inlays.

3. A spark plug comprising a shell having a threaded shank adapted to be screwed into the spark plug hole of a cylinder block and provided in proximity to the outer surface of the shank with longitudinal inlays of metal of higher heat conductivity than the metal of the shell, and a ground electrode secured to the lower end of the shank and homogeneously united to the inlays.

4. A spark plug comprising-a shell having a threaded shank adapted to be screwed into the spark plug hole of a cylinder block and provided in its outer face with longitudinally extending open sided channels, inlays positioned in said channels and of material of higher heat conductivity than the material of the shell, and an electrode secured to the shank and to the inlays heat conducting relation to the trode secured to the shank and to the inlays and having afused bond with the latter.

6. A- spark plug comprising a shell having a threaded shank adapted to be screwed into the spark plug hole of a cylinder block and provided with a plurality of longitudinal passages extending into the body of the wall of said shank from the free end thereof for more than one-half the eight of the shank, inlays in said es and f metal of better conductivity than the metal of the shell, and an electrode secured to the shell and also secured to the several inlays.

7. A spark plug comprising a shell having a threaded shank adapted to be screwed into the.

spark plug hole of a cylinder block and provided spark plug hole of a' cylinder block, inla'ys in proximity to the outer surface of the shank and extending longitudinally thereof and of metal of higher heat conductivity than the metal of the shell, and a baiiie electrode secured to the lower end of the shank and to the inlays. said inlays being protected from direct contact with the combustion charge.-

- WIILIAM E. BLOOD. 

